JP2003009091A - Digital picture communication terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a user to select a desired channel among all the program channels without a restriction in time by providing a storage device by which data where multi-channels are multiplexed by time division are recorded at a time. SOLUTION: Data reproduced by a tape head mechanism part 20 are subjected to a reproduction signal processing by a channel demodulating circuit 51, an error correcting circuit 52, a TBC 53, an error correcting circuit 54 and a frame dissolving circuit 55 and are converted into data with a prescribed data rate. Reproduction data read from a buffer memory 58 are converted into a signal format which is the same as that of a received broadcasting signal through the use of a transport encoder 59. A user selects the program channel to be reproduced by supplying a select signal from a human interface controller 60 to the buffer memory 58 in the case of reproduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal device in an image communication system such as a cable television system.

[0002]

2. Description of the Related Art In conventional television broadcasting and cable television systems (CATV), image signals transmitted from broadcasting stations are analog signals. However,
Digital CATV systems for transmitting digital image signals have been considered. This means that in addition to the progress of transmission lines and the development of communication networks, DCT (Discrete Cosine Transf
This is made possible by the practical application of high-efficiency coding technology such as orm). In other words, by using the band for one channel of the transmission of the conventional analog image signal, about 1 of the compressed image signal is used.
0 channels can be transmitted.

In digital CATV for transmitting and receiving digital image signals, not only video services similar to existing television broadcasting but also various services such as catalogs for home shopping, banking procedures, and video games,
Data can also be transmitted. With such diversification of services, it is possible that the information provided by each broadcast channel will be specialized.

In a digital image communication system such as a digital CATV, it is preferable that the receiving terminal is provided with an image storage device. This is when watching a program that is in real time, if the airtime is limited,
This is useful when you want to store other programs on air and watch them later. Further, as the image storage device, since the provided image signal is a digital signal, a storage device for the digital image signal is desirable. More specifically, the digital image signal storage device is a digital cassette tape recorder, a hard disk, a flexible disk, a semiconductor memory, or the like.

[0005]

In a digital CATV, data in which a plurality of program channels are time-division multiplexed is transmitted, and normally one of the channels is selected by a home terminal to watch or store the program. I am trying to store it in the device. However, I was unable to enjoy other channels that were not selected later.

Therefore, an object of the present invention is to provide a storage device capable of recording time-division-multiplexed multi-channel data at a time, so that all program channels can be viewed without time restriction. An object of the present invention is to provide a terminal device for digital image communication made possible.

[0007]

In order to achieve the above-mentioned object, the present invention provides a first signal for demodulating, decoding, and transmitting a received signal to an output device. A second signal processing path for modulating the demodulated signal by the processing path and the demodulation means from the first signal processing path, performing error correction coding processing, and then recording it on a recording medium. And data in which image data of a plurality of program channels is time-division multiplexed in units of packets of a predetermined byte length is input to the first signal processing path, and data of a desired program channel in the time-division multiplexed data is selected. And a means for physically recording on a recording medium.

According to a second aspect of the present invention, there is provided a first signal processing path for demodulating a received signal, decoding the signal, and sending the signal to an output device, and a demodulation means from the first signal processing path. A second signal processing path for recording the data on the recording medium after modulating the demodulated signal and performing error correction coding processing, and image data of a plurality of program channels in units of packets of a predetermined byte length Is a terminal device characterized in that the time-division-multiplexed data is input to the first signal processing path and is composed of a coupling means for recording the time-division-multiplexed data on the recording medium.

By recording the time-division multiplexed data of the received multiple program channels, any of the multiple program channels can be viewed without time constraints.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a digital CATV to which the present invention can be applied. Broadcast waves are transmitted from a broadcasting station indicated by 1 to a satellite (broadcast satellite or communication satellite) 2, and broadcast waves from the satellite 2 are received by a head end 3 provided for each service area. The headend 3 includes an antenna for receiving a broadcast wave, a reception amplifier, a video source input added as necessary, a modulator for modulating the reception broadcast wave and the video source, and a transmission line for multiplexing the modulation output. It includes a multiplexer and the like for sending to the.

A cable 5 connects the head end 3 and the home 4. The cable 5 is composed of a coaxial cable, an optical fiber, or a combination thereof, and has a tree-shaped or star-shaped wiring. A terminal 6 is provided at the home 4 of the CATV subscriber. The terminal 6 is provided with a tuner 7. The tuner 7 selectively receives a desired broadcast channel.

The CATV system to which the present invention is applicable is not limited to the one shown in FIG. For example, a plurality of program providers transmit to a satellite 2, a cable television station receives a broadcast wave from the satellite, a plurality of head ends are connected to the cable television station by optical fibers, and each head end is connected. It is also possible to have a system in which subscriber households are connected by optical fiber or coaxial cable.
Further, the present invention can be applied to digital image communication other than digital CATV, for example, a video conference system.

To facilitate the understanding of the present invention, FIG.
Of digital broadcasting signal at the head end 3 in the middle
The formation will be described with reference to FIG. The configuration of FIG. 2 is
1st to Nth broadcasting channels exist
However, multiple programs for each broadcast channel (total
Channel) is assumed to be included in the system. 31 ₁ 
~ 31_n Video source for the input terminals shown in
Are connected. This video source is transmitted through satellite 2.
Generated in the head end 3 other than
Including tatami. The video source is a digital image signal.
It is the format of the issue.

Encoders 32 _{1 to} 32 _n of high efficiency encoding, for example, MPEG are connected to the input terminals 31 _{1 to} 31 _n , respectively. The MPEG system is a high-efficiency coding system for images determined by the MPEG (Moving Picture Experts Group) of ISO (International Organization for Standardization). This is a motion-compensated interframe predictive coding. MPEG encoder 3
The output signals of 2 _{1 to} 32 ₄ are supplied to the multiplexer 33 ₁ . The multiplexer 33 ₁ forms time division multiplexed data of the first broadcast channel CH1. Multiplexer 33 ₁ as indicated by ~ 33 _N, are provided N pieces in correspondence with the broadcast channel. In the configuration of FIG. 2, program channels ch1 to ch are added to the broadcast channel CH1.
In this example, 4 is included.

Although not shown in FIG. 2, the data of each program channel is encrypted so that only the subscriber can receive it. Usually, the encryption method is specified for each program channel.

Each of the multiplexers 33 _{1 to} 33 _N time-division multiplexes the data of the channels of a plurality of programs. For example, as shown in FIG. 3, the time division multiplexed data Sx is generated from the multiplexer 33 ₁ . Figure 3
, One packet has a length of 188 bytes, and a 4-byte ID is added to the beginning of each packet. On the terminal side, program selection is performed by the select signal SLCT which becomes high level at the timing of the desired program channel. Further, in FIG. 3, since the data rates of the program channels ch1 to ch4 are equal, the packet amounts of the four channels are also equal in the time division multiplexed signal Sx. The data rate of the time division multiplexed data is set to a prescribed value (for example, 25 Mbps).

If the data rate between channels is different
Then, the amount of packets in the time division multiplexed data
Make a difference for each other. For example, if the data rate of ch1 is
If it is twice as much as that of ch2, ch3, ch4,
The number of packets of data of ch1 is other ch2, ch3, c
The number is twice that of h4. This program Chan
The data rate relationship between channels is fixed
The data rate of each program channel adaptively
By being controlled, it has the specified transmission capacity of the transmission line.
It may be possible to perform a process for effectively utilizing it. This process is
Chiplexa 33 ₁~ 33_N Made with a statistical bit allo
Application.

This is for effectively utilizing the transmission rate allowed for one broadcast channel, and each monitors the information amount of another program channel.
When the amount of information on the channels of other programs is small,
This is a process of increasing the amount of data transmission of the own channel. When this statistical bit allocation is performed, the data rate of one program channel changes within a certain range.

The ID at the beginning of each packet of time division multiplexed data includes rate information, start information, etc. of the program channel. The rate information represents the data rate of the program channel. When the above-described statistical bit allocation process is performed, the rate is variable within the same program channel, so that the maximum rate value is inserted into the ID as rate information, for example. Not only the maximum value but also the average value of the rates may be used.
The addition of this ID is performed in the multiplexers 33 _{1 to} 33 _N.

The time division multiplexed data from each of the multiplexers 33 _{1 to} 33 _N is converted to digital modulators 34 ₁ to 34 ₁ .
34 _N , and digital modulation such as PSK is performed. The carrier frequency in this case is different for each broadcast channel. And broadcast channel CH
Broadcast signals of _{1 to} CH _N are multiplexed by the frequency multiplexing circuit 35, and the broadcast signal is taken out to the output terminal 36.

Referring back to FIG. 1, an embodiment of the present invention will be described. The tuner 7 selects a desired broadcast channel. After the selected signal is demodulated by the demodulator 8, the error correction circuit 9 performs error correction to correct the error generated in the communication path. The error-corrected signal is
The signal supplied to the next conditional access 10 and encrypted (scrambled) is decrypted according to the conditions. Further, in this circuit 10 or in front thereof, a desired program channel is selected from the time division multiplexed data. The descrambled signal is usually an MPEG decoder 1
Input to 1. Here, as described above, the MPEG system is used for encoding the image data. MP
High-efficiency encoding of image data other than the EG method may be used.

The restored image data obtained from the MPEG decoder 11 is supplied to the baseband processing circuit 12. The baseband processing circuit 12 performs processing such as addition of horizontal and vertical synchronization signals, and outputs the output signal of the baseband processing circuit 12 to the monitor 13 or the printer 14. The output format of the image data from the baseband processing circuit 12 can be a RGB primary color signal, a composite color video signal, a transmission format in which a luminance signal and a carrier color signal are separated, and the like.

A digital VCR is then used to store the received digital image data. For example, an image data storage device including a digital VCR is bidirectionally connected between the conditional access 10 and the MPEG decoder 11 via a signal line 15 and an interface 16. The storage device may be coupled not only after the conditional access 10 but also before the conditional access 10. However, it is advantageous to store the decrypted data after the conditional access 10, as in FIG. This is because it is possible to perform a search by a visible image in the digital VCR, and it is possible to maintain compatibility of the recorded cassette tape.

The image data storage device comprises a buffer memory 1
7, an error correction code encoder / decoder 18, a channel encoder / decoder 19, and a tape head mechanism unit 20. The signal input to the MPEG decoder 11 is stored in the buffer memory 17 through the interface 16. Thereafter, in order to record the compressed image data on the tape, the parity of the error correction code is added by the encoder / decoder 18 and further modulated by the channel encoder / decoder 19. The recording data from the channel encoder / decoder 19 is supplied to the tape head mechanism unit 20 and recorded on the magnetic tape by the rotary head.

The tape / head mechanism unit 20 has a head attached thereto and a tape guide drum around which a magnetic tape is wound, a tape running system for running the magnetic tape along a predetermined running path, and a drum. , A drive source (for example, a motor) for rotating the capstan and the like, and a servo circuit of the drive source. With a digital VCR,
A storage device such as a hard disk or a magnetic disk may be used.

The data reproduced from the tape by the tape head mechanism unit 20 is decoded by the channel encoder / decoder 19, the error correction code is decoded by the encoder / decoder 18, and the buffer memory 1
Stored in 7. Then, it is input from the buffer memory 17 to the MPEG decoder 11 via the interface 16 and the signal line 15. Therefore, the reproduced image corresponding to the data reproduced by the image storage device can be viewed on the monitor 13 or obtained as a hard copy by the printer 14.

Further, the terminal 6 is provided with a microcomputer 21 and a modem 22. For example, the microcomputer 22 sends information indicating a desired image to the head end 3 via a telephone 23 and a telephone line 24. If the CATV system is configured as a bidirectional system, the request signal can be transmitted from the terminal 6 to the headend 3 in the opposite direction to the transmission of the broadcast signal.

FIG. 4 shows the configuration of the image signal storage device on the rear side of the interface 16 in more detail. In this embodiment, the data rate of the time division multiplexed data is standard, and the data can be recorded on the tape by the same processing as the standard data. Conditional access circuit 1
The signal from 0 is applied to the transport detection circuits 41 and P.
It is supplied to the LL 42 and, for example, a packet of 188 bytes is decoded. The transport detection circuit 41 detects the ID added to each packet. This ID
Is an ID recorded in the multi-program, an ID representing each rate of the recorded program, its title, and the like. The PLL 42 in the input section is necessary for clock recovery when the clock is not transferred through the interface 16.

A servo reference signal for recording is obtained from the clock reproduced by the PLL 42, and this is input to a mechanism controller 45 composed of a microcomputer.
On the other hand, the data passed through the transport detection circuit 41 is
The data is written in the buffer memory 46 at the timing designated by the rate information. Image data is read from the buffer memory 46 at the timing of the recording system of the digital VCR.

The data read from the buffer memory 46 is subjected to signal processing for trick mode reproduction operation by the trick mode processing circuit 47 and then supplied to the framing circuit 48. The trick mode processing circuit 47
When recording compressed image data of the MPEG system, processing is performed in consideration of trick modes such as high speed reproduction and slow reproduction. That is, the trick mode processing circuit 47 always records the data of the intra frame (the encoded data of the intra frame exists in every predetermined frame in the MPEG system) on the track traced by the rotary head during the high speed reproduction, for example. Control.

The framing circuit 48 converts compressed video data, PCM audio signals, subcodes, etc. into data of a predetermined recording format. This recording format will be described later. In the framing circuit 48, the ID recorded in the multi-program, the ID representing the rate of each recorded program, and the information such as the title are inserted into, for example, the AUX area in the video recording area, and the ID is recorded on the tape. Recorded in. Framing circuit 4
8 output signals are supplied to the recording processing circuit 49. The recording processing circuit 49 performs processing such as encoding of error correction code and channel modulation, and from this, recording data (for example, about 44 Mbps) is generated.

The recording data from the recording processing circuit 49 is supplied to the tape head mechanism section 20, and the recording data is recorded on the magnetic tape as an oblique track. The mechanism controller 45 controls the tape head mechanism unit 20 to record the recording data. Further, a subcode processing circuit 50 is provided, and the subcode is supplied to the recording processing circuit 49 and recorded in a prescribed subcode recording area. The start ID is supplied to the subcode processing circuit 50 and recorded in the subcode area. The rate information may be recorded in the sub code area.

At the time of reproduction, the ID of the multi-program is read and the tape head mechanism section 20 is set to the normal reproduction rate. The data reproduced by the tape head mechanism unit 20 is supplied to the channel demodulation circuit 51 and demodulated for channel modulation. An error correction circuit 52 using an error correction code (C1 code) is connected to the channel demodulation circuit 51. The structure of the error correction code of the digital VCR will be described later. The output of the error correction circuit 52 is supplied to the TBC 53, and the time axis variation of the reproduced data is removed. The TBC 53 further sends the data converted to a predetermined data rate according to the rate information from the mechanism controller 56 to the subsequent stage.

The output of the TBC 53 is the error correction code (C2
(Code) error correction circuit 54, and the error is corrected by the C2 code. The data after error correction by the error correction circuit 54 is supplied to the frame decomposition circuit 55, and compressed video data, audio data, subcode, etc. are separated. Further, in the frame disassembling circuit 55, the rate information recorded in the video AUX is separated.

The rate information separated by the frame disassembling circuit 55 is supplied to the mechanism controller 56, and the mechanism controller 56 uses this rate information so as to match the recorded rate with the tape head mechanism section 20. Control TBC53. Buffer memory 5
The reproduction data read from the data No. 8 is supplied to the transport encoder 59 and converted into the same signal format as the received broadcast signal.

In this way, the reproduced data is MPEG
The transport encoder 59 processes the reproduction data so that it can be read by the decoder 11, and the processed data is sent out. This reproduction data is MPEG decoder 1
1 to restore the image.

At the time of this reproduction, the program channel to be reproduced is selected by the user. This is done by supplying the select signal from the human interface controller 60 to the buffer memory 58. In the buffer memory 58, only the data of the selected program channel is stored in the transport encoder 5
9 to the MPEG decoder 11 and monitor 13
, The image of the program channel selected by the user is reproduced.

The above-described tape head mechanism section 20 will be described more specifically. As an example, a pair of magnetic heads are attached to the rotating drum at a facing interval of 180 °. The circumference of the drum is slightly larger than 180 °,
Or, the magnetic tape is wound diagonally with a slightly small winding angle. Therefore, the two magnetic heads alternately contact the magnetic tape. Further, it is also possible to use a configuration in which two magnetic heads are attached to the drum in an integrated structure. In this case, two magnetic heads trace the magnetic tape at the same time.

The gap extension directions (referred to as azimuth angles) of the pair of magnetic heads are different.
For example, an azimuth angle of ± 20 ° is set between the two magnetic heads. Due to this difference in azimuth angle, adjacent tracks formed on the magnetic tape are formed by magnetic heads having different azimuth angles. Therefore, during reproduction, the amount of crosstalk between adjacent tracks can be reduced due to azimuth loss.

The track format of the digital VCR will be described. FIG. 5 shows an array of data recorded on one track. In FIG. 5, the left end of the track is the head entry side, and the right end thereof is the head separation side. Also, no data is recorded in the margin and IBG (inter block gap).

Next, details of signals recorded in each area in one track will be described. (1) ITI Area As shown in the enlarged portion of FIG. 5, the ITI area has a 1400-bit preamble and 1830-bit SSA (Start-Sync BlockAre).
a), 90-bit TIA (Track Information)
ation Area) and a 280-bit postamble. Here, the preamble has a function such as a run-in of the PLL at the time of reproduction, and the postamble has a role of earning a margin.

Both the SSA and the TIA are composed of a SYNC block having a data length of 30 bits as a unit, and the first 10 blocks in each SYNC block.
20 following bit SYNC signal (ITI-SYNC)
Data is recorded in the bit part. As the contents of this data, sync block numbers (0 to 60) are recorded in the SSA, and 3-bit APT information, 1
Bit recording mode (SP / LP) information and 1-bit pilot frame information indicating a reference frame of the servo system are recorded. The APT is ID data that defines the data structure on the track.

Since each sync block in the ITI area is recorded at a fixed position on the magnetic tape, for example, the 61st SY of SSA from the reproduced data.
By using the position where the NC signal pattern is detected as a reference for defining the post-recording position on the track, the position to be rewritten during post-recording can be defined with high accuracy, and good post-recording can be performed.

(2) Audio area The audio area for recording the PCM audio signal is
As shown in the enlarged portion in FIG. 5, it has a preamble and a postamble before and after it, where the preamble is a run-up for PLL lock-in and a pre-SYNC for pre-detection of an audio SYNC block.
The postamble includes a post-SYNC for confirming the end of the audio area and a guard area for protecting the audio area during video data post-recording.

The pre-SYNC is the SYNC block 2
From the individual, the post SYNC is composed of one SYNC block. Then, the SP / LP identification byte is recorded at the 6th byte of the pre-SYNC. This is FF
When h represents SP and 00h represents LP, and when the SP / LP flag recorded in the above-mentioned ITI area is unreadable, the value of the SP / LP identification byte of this pre-SYNC is adopted. Also, FFh is recorded as dummy data in the 6th byte of post SYNC.

The audio data recorded between the preceding and following amble areas is framing-added and further parity-added. FIG. 7 shows a format in which parity is added by performing this framing.

In FIG. 7, 72 bytes of audio data are added with 5 bytes of audio accompanying data (referred to as audio AUX data) at the beginning to form 1 block of 77 bytes of data, which is vertically divided into 9 bytes. Framing is performed by stacking blocks, and an inner code parity C1 and an outer code parity C2 are added to this. That is,
For 77 bytes located horizontally, (85,7
7) The Reed-Solomon code is encoded to form an 8-byte inner code parity (C1 parity).
The (14,9) Reed-Solomon code is encoded with respect to 9 bytes located in the vertical direction to form a 5-byte outer code parity (C2 parity). The data to which these parities are added is read in units of blocks, a 3-byte ID is added to the head side of each block, and a 2-byte SYNC signal is added to the data, and the data shown in FIG.
1SYN with a data length of 90 bytes as shown above
It is converted into the signal of the C block. Then, this signal is recorded on the tape.

(3) Video area A video signal encoded by the MPEG system is recorded,
The video area has the same preamble and postamble as the audio area as shown in the enlarged portion of FIG. However, it is different from the audio area in that the guard area is formed longer.

The video signal for one track to be recorded is
In the framing circuit 48, framing is performed together with video accompanying data (this is referred to as video AUX data) for each one track of data, and then an error correction code is added in the recording processing circuit 49. FIG. 6 shows a format in which parity is added by performing this framing.

As shown in FIG. 6, video data of 77 bytes is vertically stacked in 135 (5 × 27) blocks, and video AUX data of 3 blocks is added to the upper and lower parts. Here, in a 5SYNC block, that is, in a buffering unit, 30D
It is assumed that the data for the CT block is included.

Then, the (85,77) Reed-Solomon code is encoded with respect to the 77 bytes located in the horizontal direction, and the parity of the inner code of 8 bytes (C1 parity) is obtained.
Is generated, the outer code of the (249, 138) Reed-Solomon code is encoded with respect to 138 bytes located in the vertical direction, and the parity of the outer code of 11 bytes (C2
Parity) is generated. The data to which these parities are added is read in units of blocks, a 3-byte ID is added to the beginning of each block, and a 2-byte SYNC signal is added to the data, which is shown in the upper part of FIG. Is converted into a signal of 1 SYNC block having a data length of 90 bytes. Then, this signal is recorded on the tape.

In the framing format described above, since 27 buffering units representing one track of video data are data for 810 DCT blocks, data for one video frame (DCT).
(8100 blocks) will be recorded as 10 tracks.

(4) Subcode Area The subcode area is an area mainly provided for recording information for high speed search. A subcode is generated by the subcode processing circuit 50. As shown in FIG. 8, the subcode area includes 12 SYNC blocks having a data length of 12 bytes, and a preamble and a postamble are provided before and after the SYNC block. However, unlike the audio area and the video area, the pre-SYNC and post-SYNC are not provided. Then, each of the 12 SYNC blocks is provided with a data section for recording a 5-byte subcode. Also, as the parity for protecting this 5-byte subcode, (14, 10)
Reed-Solomon code is used and inner code parity C1
Is formed.

The recording format on the above-mentioned tape is M
It is used for recording PEG-encoded video data, PCM audio signals and subcodes.
In a digital CATV system, data to be provided may be data (referred to as general data) such as program data for a computer, in addition to video data, as in the case of video games, computer networks, and the like.
The format used for recording / reproducing such general data will be described below.

First, as shown in FIG. 9, general data is
The total tape length L of the cassette tape is divided into four equal parts, and the length is recorded as 1/4 L of the preceding part. For example, 2.95 GB of general data can be recorded in the preceding portion. By thus recording the general data collectively on the preceding portion of the tape, the general data can be easily accessed. For example, when general data and video / audio data are mixed and recorded in the tape longitudinal direction, it takes time to access the general data, and there is a problem that the processing time for downloading the data becomes long. The total amount of general data that can be recorded on a tape is very large, and a predetermined amount of it is usually downloaded to the memory.

Video and audio data will be recorded after (1/4) L from the front end of the tape. Therefore, when recording video and audio data before general data, it is necessary to feed the tape to that position based on the count value of the tape counter, for example. In this case, the recording start position of video and audio data may change depending on the tape feeding accuracy. Therefore, a guard area is provided between the general data recording area and the video and audio data recording areas. The general data may be collectively recorded at the end of the (1/4) L length near the end of the tape.

Further, as can be seen from the above-mentioned track format, there is an audio area at the beginning of the track. Also for this audio area,
You may make it record general data.

Also in the digital CATV system shown in FIG. 1, it is conceivable to receive general data in addition to continuous data such as video and audio data. The type of this data is indicated by the code in the ID of each packet, for example. The mechanism controller 45 in FIG. 4 controls the tape head mechanism unit 20 when the data received and selected indicates that the selected data is continuous data, and the data recording area is continuous. It is controlled so that it becomes the recording area of the dynamic data. If the selected data is general data, the recording position is moved to the general data recording area at the leading or trailing end of the tape.

The recording format of general data will be described. As shown in FIG. 10, a data structure in which 27 blocks are vertically stacked is treated as a basic unit. This basic unit is called a universal unit. The universal unit includes 2079 bytes of general data, but dummy data may be added to include 2048 bytes of general data for convenience of handling the data. Furthermore, 9 obtained by dividing the universal unit into three equal parts
Each SYNC block is called a subunit.

For the data structure of this universal unit, as shown by the diagonal lines in FIG.
AUX data of block is added to the upper side, and 1SYNC
The AUX data of the block is added to the lower side. And
For 77 bytes located horizontally, (85,7
7) The Reed-Solomon code is encoded, and the parity (C1 parity) of the 8-byte inner code is generated. For 138 bytes located in the vertical direction, (249, 13
8) The outer code of the Reed-Solomon code is coded and 1
A 1-byte outer code parity (C2 parity) is generated.

Further, 27 blocks of general data are divided into sub-units consisting of 9 blocks, the header and AUX data are added to the first block of the first sub-unit, and the remaining sub-units are added. AUX data is added to the first block. The data structure of FIG. 11 is the same as the data structure of the video data shown in FIG. Therefore, as shown in FIG. 13, it can be recorded in the video area in one track formed on the tape in the same manner as the video data.

When recording general data in the audio area, a unit of subunit is recorded as shown in FIG. Nine blocks are vertically stacked, and (85,77) Reed-Solomon code is encoded for 77 bytes located in the horizontal direction to form an 8-byte inner code parity (C1 parity). The (14,9) Reed-Solomon code is encoded for 9 bytes located in the direction, and the parity (C2
Parity) is formed. If necessary, the first 5 bytes of each block are used as an area for AUX data. The data structure of FIG. 12 is the same as that of the audio data shown in FIG. 8, and general data can be recorded in the audio area on the start end side of the track.

Further, general data may be recorded by a multi-track recording system in which one track is divided. Inner code and outer code are encoded with respect to the universal unit in which 27 blocks shown in FIG. 14 are stacked. This data structure (38 blocks) is recorded by the multi-track method. For example, as shown in FIG.
1 so that there is a guard area between each divided track
The track is divided into four, and general data is recorded for each divided track. In that case, a sub-code area indicated by diagonal lines is added to each divided track.

As described above, by recording general data on the tape in units of the universal unit shown in FIG. 10, framing and error correction code processing can be shared with video and audio data. Furthermore, in the case of general data, unlike video and audio data, errors cannot be corrected by interpolation processing, so it is preferable to perform stronger error correction coding. In this case, it is necessary to keep the advantage of sharing the processing with the video and audio data described above. The improvement of the error correction capability based on such consideration will be described with reference to FIG.

FIG. 16 shows 10 tracks of general data recorded in the video and audio areas as shown in FIG. Oblique tracks are shown as vertical tracks for simplicity. In the video area,
6, general data is recorded with the data structure shown in FIG. 11, and general data is recorded in the audio area as shown in FIG. The number of 10 tracks is the number of tracks required to record one frame of data in the case of video data.

Then, the third error correction coding is performed with 10 tracks as one code unit. That is, FIG.
As shown in FIG. 6B, the previously traced 7 tracks are used as recording tracks for general data, and the remaining 3 tracks are used as third parity (referred to as C3 parity) recording tracks. More specifically, C1 and C2
Regarding general data or AUX data excluding parity, bytes existing at the same position in the data array are extracted from 7 tracks, and (1
0,7) Reed-Solomon code is encoded. The 3-byte C3 parity is recorded at the corresponding position on the 3 tracks. According to the method of further adding the third error correction coding as shown in FIG. 16B, error correction can be performed even when all the data in one track has an error. In addition, C1
The parity and the C2 parity may be error-correction coded similarly to the data.

FIG. 16C shows another method of enhancing the error correction capability, namely double recording. The same general data is double recorded on every two adjacent tracks. General data recorded on one track is equally divided into D _i and D _{i + 1} , one divided data D _i is recorded in the first half of the previous track and the latter half of the rear track, and the other divided data D _i is recorded. Record ₊₁ in the second half of the front track and in the first half of the back track. For example, the divided data D ₀ is recorded in the first half of the previous track and the latter half of the rear track, and the other divided data D ₁ is recorded in the latter half of the previous track and the first half of the rear track. Double recording enables error correction by the collation method. In addition, the method of FIG. 16C can enhance the error correction capability for scratches in the tape longitudinal direction.

In the above-described embodiment, the data rate recorded by the tape head mechanism unit 20 is standard, for example, 25 Mbps. However, this is the rate of compressed image data before recording processing,
The recording data rate recorded on the tape is about 44 Mbps because other data is added and channel modulation is performed.

[0069]

According to the present invention, by recording the data in which the received multiple program channels are time-division multiplexed, it is possible to view any of the multiple program channels without time constraints. .

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a digital CATV system to which the present invention can be applied.

FIG. 2 is a block diagram of an example of a transmitting side in a digital CATV system.

FIG. 3 is a waveform diagram showing an example of transmission data and a program channel selection signal.

FIG. 4 is a block diagram of a main part of an embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining an example of a track format on a tape.

FIG. 6 is a schematic diagram for explaining a data structure of video data.

FIG. 7 is a schematic diagram for explaining a data structure of audio data.

FIG. 8 is a schematic diagram for explaining the data structure of subcode data.

FIG. 9 is a schematic diagram for explaining a general data recording method.

FIG. 10 is a schematic diagram for explaining a basic unit of a data structure of general data.

FIG. 11 is a schematic diagram for explaining an example of a data configuration of general data.

FIG. 12 is a schematic diagram for explaining another example of the data structure of general data.

FIG. 13 is a schematic diagram for explaining an example of a general data recording method.

FIG. 14 is a schematic diagram for explaining another example of the data structure of general data.

FIG. 15 is a schematic diagram for explaining another example of the recording method of general data.

FIG. 16 is a schematic diagram for explaining one example and another example of error correction encoding for general data.

[Explanation of symbols]

3 headend 6 Terminals provided at home 10 conditional access 11 MPEG decoder 13 monitors 17 buffer memory 20 Tape head mechanism 45 Mechanism controller 46 buffer memory 55 Frame disassembly circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiji Kanata             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 5C025 DA01                 5C053 FA22 GA11 GB06 GB15 GB21                       GB37 JA21 LA06 LA07                 5D044 AB07 BC08 CC09 DE14 EF10

Claims (6)

[Claims] 1. A first signal processing path for demodulating a received signal, decoding the signal, and sending it to an output device, and a demodulated signal is modulated by a demodulation means after the first signal processing path. Then, after performing the error correction coding process, the second signal processing path for recording on the recording medium and the image data of a plurality of program channels in units of packets of a predetermined byte length are time-division multiplexed. Data is input to the first signal processing path and means for selectively recording data of a desired program channel in the time division multiplexed data on the recording medium. . 2. A demodulated signal is demodulated by a first signal processing path for demodulating a received signal, decoding the signal, and sending it to an output device, and demodulation means after the first signal processing path. Then, after performing the error correction coding process, the second signal processing path for recording on the recording medium and the image data of a plurality of program channels in units of packets of a predetermined byte length are time-division multiplexed. Data is input to the first signal processing path, and the terminal device comprises a coupling means for recording the time division multiplexed data on the recording medium. 3. The terminal device for digital image communication according to claim 1, wherein the image data of a plurality of program channels is time-division multiplexed data, and the data of each program channel is encrypted. The terminal device is characterized in that it is supplied to the second signal path after decryption. 4. The terminal device for digital image communication according to claim 1, wherein one broadcast channel includes data in which image data of a plurality of program channels are time-division multiplexed, and each broadcast channel. A terminal device, wherein data is encrypted by the same method, and the data is supplied to the second signal path after decryption. 5. The terminal device for digital image communication according to claim 1 or 2, wherein the first signal processing path and the second signal processing path are integrated together. 6. The terminal device for digital image communication according to claim 1 or 2, wherein the first signal processing path and the second signal processing path are configured separately. apparatus.